The pathophysiological triad is composed of etiology (cause of the disease), valve lesions (resulting from the disease) and valve dysfunction (resulting from the lesions). These distinctions are relevant because long-term prognosis depends on etiology, whereas treatment strategy and surgical techniques depend on valve dysfunctions and lesions respectively.

Carpentier’s functional classification of mitral valve disease is used to describe the mechanism of valvular dysfunction.This classification is based on the opening and closing motions of the mitral leaflets. Valvular dysfunction may present four functional types in the setting of mitral regurgitation. Patients with type I dysfunction have normal leaflet motion with the free edges of the leaflets positioned 5 to 10 mm below the plane of the annulus. Mitral regurgitation in these patients is due to annular dilatation, or leaflet perforation or tear. There is an increased leaflet motion in patients with type II dysfunction with the free edge of one or more leaflets overriding the plane of the annulus during systole (leaflet prolapse). The most common lesions leading to type II dysfunction are chordae elongation or rupture, and papillary muscle(s) elongation or rupture. Patients with type IIIa dysfunction have a restricted leaflet motion during both diastole and systole. The most common lesions are leaflet thickening retraction,chordae thickening shortening or fusion, and commissural fusion encountered in rheumatic valve disease. Mitral regurgitation is usually associated with varying degrees of mitral stenosis. The mechanism of mitral regurgitation in Type IIIb dysfunction is restricted leaflet motion during systole. Left ventricular enlargement leading to apico-lateral papillary muscle displacement and chordae tethering causes this type of valve dysfunction. From Carpentier A, Adams DH, Filsoufi F. Carpentier’s Reconstructive Valve Surgery. Saunders (Elsevier), 2010.

The functional classification is further refined by segmental valve analysis which allows the precise localization of leaflet dysfunction which is of significant importance while performing reconstructive surgery.The mitral valve is ided into 8 segments. Antero-lateral and postero-medial commissures are two segments. Two indentations on the posterior leaflet ide this structure into 3 anatomically distinct scallops. The three scallops of the posterior leaflet are identified as
P1 (anterior scallop), P2 (middle scallop), and P3 (posterior scallop). The three corresponding segments of the anteriorleaflet are named A1 (anterior segment), A2 (middle segment), and A3 (posterior segment).
From Carpentier A, Adams DH, Filsoufi F. Carpentier’s Reconstructive Valve Surgery. Saunders (ElFrom Carpentier A, Adams DH, Filsoufi F. Carpentier’s Reconstructive Valve Surgery. Saunders (Elsevier), 2010. Preoperatively, the functional classification and segmental analysis allow the echocardiographer to determine the precise localization of valvular dysfunction in patients with mitral valve disease. Intraoperatively, it enables the surgeon to proceed to a full analysis of valvular lesions in the segments where a dysfunction has been deteFrom Carpentier A, Adams DH, Filsoufi F. Carpentier’s Reconstructive Valve Surgery. Saunders (Elsevier), 2010

From Carpentier A, Adams DH, Filsoufi F. Carpentier’s Reconstructive Valve Surgery. Saunders (Elsevier), 201Valvular dysfunctions and corresponding lesions and etiologies are summarized here. It is remarkable to notify the contrast between the complexity of valvular lesions and the simplicity of resulting valvular dysfunction(s).

Addendum:
Several varieties of prolapse require additional nosologic clarification:
Near prolapse: A condition in which the free edge of the leaflet approaches the plane of the annulus without overriding it during systole. Leaflet apposition is not perfect; there is, however, no valvular regurgitation. This condition can worsen overtime leading to
leaflet prolapse and significant mitral regurgitation.

Pseudo prolapse:
A condition in which the free edge of the anterior leaflet is above the free edge of the posterior leaflet without overriding the plane of the annulus. Seen in type IIIb dysfunction, the jet of mitral regurgitation is posteriorly directed on echocardiography.

Billowing leaflet:
Defined by the systolic protrusion of the belly of the leaflet into the left atrium due to excess leaflet tissue while the free edge remains below the plane of the annulus. Seen in patients with Barlow’s disease, billowing leaflet(s) does not cause valvular regurgitation. It can, however, be complicated with leaflet prolapse secondary to chordae elongation rupture, leading to mitral regurgitation.

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